In printers containing ink reservoirs, the ink reservoir is ordinarily maintained under a sub-atmospheric or negative pressure so that ink will not leak or drool from the print head. Various types of ink reservoirs may be used including onboard ink reservoir cartridges which are mounted on the moveable printer carriage and remote or offboard ink reservoirs from which ink is brought to the print head on the printer carriage by tubing. In the onboard cartridges a polymer foam is ordinarily provided in the ink reservoir so that the capillary action of the foam will prevent ink from drooling from the print head. Polymeric foams of the type typically used for this purpose are non-biodegradable and thus cause environmental problems whenever a previously used cartridge is emptied and thrown away. In addition, the use of industrial foam in the ink reservoir restricts the operating pressure range of the ink cartridge and such foams ordinarily leave a chemical residue which is incompatible with and/or reacts adversely with printer ink. Similarly, the relatively long tubing used to convey ink from an offboard pressure reservoir to a printing head is not easily adaptable to deliver ink to the print head at different printing pressure ranges.
A collapsible ink reservoir for an inkjet printer is disclosed in U.S. Pat. No. 4,422,084 issued Dec. 20, 1983 to Saito. Negative pressure is maintained in a polypropylene ink bag by various types of springs which bias the bag walls apart from each other. The springs may be mounted inside of or externally of the ink bag but the spring pressure regulator construction does not result in substantially complete emptying of the ink bag and the bag itself is not carried on a printer carriage.
One example of an improved onboard ink reservoir cartridge is disclosed in U.S. patent application Ser. No. 07/717,735, filed Jun. 19, 1991, U.S. Pat. No. 5,359,353 entitled SPRING-BAG PRINTER INK CARTRIDGE WITH VOLUME INDICATOR filed by David S. Hunt and W. Bruce Reid and assigned to the assignee of the present invention. The cartridge disclosed in that application basically comprises a rectangular housing containing a flexible bag of ink, an ink filter and a print head which receives ink from the filter. A spring inside of the bag of ink urges its flexible walls apart from each other thus maintaining a negative or sub-atmospheric pressure in the reservoir which is overcome as ink is emitted from the print head.
Also of interest are prior co-pending U.S. patent applications Ser. No. 07/929,615, filed Aug. 2, 1992 by Kaplinsky, et al. entitled COLLAPSIBLE INK RESERVOIR STRUCTURE AND PRINTER INK CARTRIDGE; and Ser. No. 07/928,811, filed Aug. 12, 1992 by Khodapanah, al. entitled INK PRESSURE REGULATOR FOR A THERMAL INK-JET PRINTER; both owned by the assignee of the present application.
Further developments of this collapsible bag technology are disclosed in United States patent applications filed on Dec. 22, 1992 entitled METAL COVER ATTACHMENT TECHNIQUE FOR THERMAL INKJET PEN by inventors Dale D. Timm, Jr., et al., Ser. No. 07/994,810; RIGID LOOP CASE STRUCTURE FOR THERMAL INK-JET PEN by inventors David W. Swanson, et al., Ser. No. 07/994,808; TWO MATERIAL FRAME HAVING DISSIMILAR PROPERTIES FOR THERMAL INK-JET CARTRIDGE by inventors David W. Swanson, et al., Ser. No. 07/995,221; and DOUBLE COMPARTMENT INK-JET CARTRIDGE WITH OPTIMUM SNOUT by inventors David W. Swanson, et al. all owned by the assignee of the present invention.
Further developments of this collapsible bag technology are disclosed in United States patent applications filed on the same day as this application entitled COLLAPSIBLE INK RESERVOIR AND INK-JET CARTRIDGE WITH PROTECTIVE BONDING LAYER FOR THE PRESSURE REGULATOR by inventors James H. Sykora, et al., Ser. No. 07/997,207; and NEGATIVE PRESSURE INK DELIVERY SYSTEM by inventors George T. Kaplinsky, et al., Ser. No. 07/995,851 both owned by the assignee of the present invention.
In order to provide an acceptable printer ink cartridge utilizing a collapsible ink bag or reservoir, there is a need for an ink bag or reservoir that is as flexible as possible in order to allow the reservoir bag to collapse in unimpeded manner to minimize stranded ink in the reservoir and to maintain the desired degree of negative pressure within the reservoir bag. The reservoir bag must also provide a strong moisture and gas barrier in order to prevent water loss form the reservoir, and prevent external contaminants such as air from entering the reservoir. Suitable materials for the reservoir should be materials capable of allowing the reservoir's peripheral edges to be sealed in order to form an ink reservoir that does not separate during normal use. In addition, the material used for the reservoir should be easily sealable in order to prevent leakage or migration of the ink from of the reservoir and chemically compatible and non-reactive with the ink contained therein.
Further, the reservoir should be puncture resistant because despite careful handling and packaging, the relatively rigid pressure regulator sideplates may during shipment, handling, or installation puncture the thin flexible reservoir walls. Although such puncturing is quite rare, this puncturing must be totally avoided without unduly thickening the reservoir walls so as to inhibit ink from being completely exhausted from the collapsible reservoir.
Finally, by providing a reservoir bag with adequate moisture/gas barrier allows the ink cartridges to be packaged without any special barrier packaging. This special barrier packaging currently requires packaging in sealed aluminum containers. Special packaging for protection from physical damage to the ink reservoir currently involves a plastic insert within the aluminum barrier protection. Elimination of this special packaging provides both environmental and cost benefits.